1. Field of the Invention
This invention relates to an electromagnetic flowmeter detector.
2. Description of the Related Art
For reference, a conventional electromagnetic flowmeter detector is shown in FIGS. 1(a) and 1(b), and its coil is shown in FIG. 2. In these drawings, 1 is a mating flange, 2 is a locking bolt, 3 is an outer casing, 4 is a coil, 5 is an excitation line, 6 is a signal line, 7 is a measuring tube made of a non-magnetic pipe, 8 is an electrode, 10 is a lining, and 11 is a packing.
As shown in FIGS. 1(a) and 1(b), the conventional electromagnetic flowmeter detector has a structure whereby the thin-wound coil 4 as shown in FIG. 2 is packaged in a narrow space between the measuring tube 7 and the outer casing 3. In order to ensure an effective dimension W, the thin-wound coil 4 is in need of waste dimensions L.sub.1, L.sub.2 (L.sub.1 =L.sub.2) similar to W. As a result, the length L.sub.c of a magnetic field generating portion increases and an inter-face distance is lengthened as shown in FIG. 1(a). In case of an increased inter-face distance, it is difficult to eliminate materials adhered on the lining inner surface of the measuring tube, and it is difficult to mount the detector in a narrow spot.
Further, the conventional coil of length L.sub.c shown in FIG. 2 is naturally long with respect to the length of the coil wire and thus its DC resistance becomes large. If the wire were made thick in order to decrease the resistance, it could not be stored in a coil accommodating space. This difficulty becomes more pronounced with an increased in diameter, and thus an electromagnetic flowmeter detector of more than 150 mm in diameter could not be easily manufactured in the prior art. If the detector were manufactured with such poor resistance properties, the rise time of a magnetic flux is delayed because of the foregoing increased DC resistance, and such detectors could be used only in limited circumstances.